Avo Modeling Based Rock Physics And Elastic Impedance Analysis Of Kadanwari Area, Lower Indus Basin, Pakistan (T-1549) (MFN 6867)

Abstract

The study area is located in Kadanwari Gas Field situated in Khairpur district, Sindh Pakistan. Geologically the study area lies in Middle Indus Basin and comprises of both structural and stratigraphic traps along with a complete petroleum system. Structural interpretation of six migrated seismic sections followed by generation of time contour maps, revealed the presence of normal faults in the area which serve as a trapping mechanism for hydrocarbons. Using available well log data, petrophysical analysis has been conducted in well Kadanwari-03 and Kadanwari-10, which confirms the presence of reservoir in lower Goru sands at E-sand level. Elastic properties i.e. Lambda-Rho, Vp/Vs ratio, Poisson’s ratio and impedance logs are computed at Kadanwari-03 and Kadanwari-10 using rock physics analysis. These elastic properties are cross–plotted to differentiate the lithology and fluid in the target zone which is E-sand of Lower Goru formation. The result showed that lower values of Lambda-Rho, Vp/Vs ratio and impedance values correlated with areas containing hydrocarbons. The cross-plot analyses successfully distinguished between fluids and lithology effect in the area, these were subsequently confirmed by AVO modeling. AVO modelling of the reservoir response concluded that gas saturation has some influence on seismic reflection amplitude of the E sand interval. Results from this study show significant amplitude increase with offset for a gas-saturated reservoir as compared to brine-saturated reservoir. AVO class 2 usually shows increase in amplitude at the far offset as compared to near offsets therefore elastic impedance is used to obsersve AVO effect by generating elastic impedance logs at various angles of incidence. In conclusion, the use of additional seismic attributes (elastic impedance and extended elastic impedance) helps to achieve a better reservoir characterization especially in a class 2 environment.